Synchronization systems are widely employed within telephone offices, for example, to distribute synchronization signals to various digital circuit elements that employ the synchronization signals in the timing, transmission, reception, and routing of signals. A typical office, such as a telephone central office, includes a central synchronization generator, such as a building integrated timing supply (BITS) clock, which generates and distributes the synchronization, or clock, signals throughout the office to individual network elements within the office. Conventional clock distribution systems often employ DS1 or composite clock timing signals which operate, respectively, at 1.544 Mb/s and 8/64 kb/s. In small offices, this mode of timing distribution is both economical and adequate. In larger offices, offices that employ in the tens of network elements or more, the management and routing of the timing cables can prove to be challenging.
That is, in a conventional centralized distribution system such as this, individual twenty-two gauge twisted wire pair shielded cables carry the desired clock signals between each network element and the BITS clock. Each of these cables is typically limited in length to six hundred and fifty five feet. Such length restrictions may severely limit the size of office that may be served by such a conventional synchronization system, with larger offices requiring the addition of another BITS clock. The additional BITS clock must also be synchronized with the first BITS clock in order to avoid timing loops within the office. Not only is there a significant capital expense associated with the addition of a BITS clock, the increased maintenance costs can also be significant. Additionally, noise and crosstalk electromagnetically induced on the cables can seriously degrade the performance of such a system and the number of taps, or ports for connection with network elements, is limited by the number of ports available at the centralized clock source. Furthermore, since cabling in such facilities is often routed through cabling “troughs”, the addition of an network element means more cable must be routed through the troughs. Not only may the addition of cables to these troughs exceed the physical capacity of the troughs, maintenance of cables within the troughs could be severely compromised by the forcing too many cables into a trough. That is, since all the clock distribution cabling is routed to a centralized location, the physical bulk of the cabling may prevent the addition of more cabling and may hinder attempts to maintain the existing cabling.
A synchronization system that is relatively impervious to electromagnetic interference, that is readily capable of distributing clock signals substantially farther than six hundred and fifty five feet, and that provides for modular growth to accompany the expansion of an associated office system is therefore highly desirable.